package org.nerve.boot.util;

import org.apache.commons.lang3.StringUtils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * MD5工具类.
 */
public class MD5Util {
    /**
     * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,apache校验下载的文件的正确性用的就是默认的这个组合
     */
    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6','7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
    protected static MessageDigest messagedigest = null;
    static {
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }
    /**
     * 获取文件MD5值
     * @param file  File
     * @return  md5
     * @throws IOException  异常
     */
    public static String encode(File file) throws IOException {
        return encode(new FileInputStream(file));
    }

    public static String encode(InputStream is) throws IOException {
        byte[] buffer = new byte[1024];
        int numRead = 0;
        while ((numRead = is.read(buffer)) > 0) {
            messagedigest.update(buffer, 0, numRead);
        }
        is.close();
        return bufferToHex(messagedigest.digest());
    }

    /**
     * 密码字符串MD5加密 32位小写
     * @param str   string
     * @return      md5
     */
    public static String encode(String str){
        if(StringUtils.isEmpty(str)){
            return "";
        }
        byte[] buffer=str.getBytes();
        messagedigest.update(buffer);
        return bufferToHex(messagedigest.digest());
    }

    public static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }

    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换
        // 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同
        char c1 = hexDigits[bt & 0xf];// 取字节中低 4 位的数字转换
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }

    private static final String toHex(byte hash[]) {
        if (hash == null) {
            return null;
        }
        StringBuffer buf = new StringBuffer(hash.length * 2);
        int i;

        for (i = 0; i < hash.length; i++) {
            if ((hash[i] & 0xff) < 0x10) {
                buf.append("0");
            }
            buf.append(Long.toString(hash[i] & 0xff, 16));
        }
        return buf.toString();
    }

    public static String hash(String s) {
        try {
            return new String(toHex(encode(s).getBytes("UTF-8")).getBytes("UTF-8"), "UTF-8");
        } catch (Exception e) {
            return s;
        }
    }
}